如何在 JOptionPane 中格式化字符串

Question

我发现并修复了我的错误，我格式化了两次。

我正在尝试使用 JOptionPane 显示美元金额，但由于它是双精度数，我在小数点后得到了额外的数字。在 JOptionPane 中如何格式化？我尝试使用 String.format 但当我运行时出现错误；

Exception in thread "main" java.util.MissingFormatArgumentException: Format specifier '%.2f'
 at java.util.Formatter.format(Unknown Source)
 at java.util.Formatter.format(Unknown Source)
 at java.lang.String.format(Unknown Source)
 at CouponCalc.main(CouponCalc.java:38)

这是我的代码；

import javax.swing.JOptionPane;
public class CouponCalc {
    public static void main(String[] args) {

        double groceriesCost, discount;
        double tier1=.08, tier2=.1, tier3=.12, tier4=.14; //coupon percentages for easy adjustment

        groceriesCost = Double.parseDouble(JOptionPane.showInputDialog("Enter cost of groceries."));

        if (groceriesCost<0)
            {
                JOptionPane.showMessageDialog(null, "Invalid Entry"); //TODO implement loop
                System.exit(0);
            }

        else if (groceriesCost>=0 && groceriesCost<=9.99)   //No coupon
            JOptionPane.showMessageDialog(null, "You do not qualify for any coupons.)");


        else if (groceriesCost>=10.00 && groceriesCost<=59.99) //tier 1 coupon  
            JOptionPane.showMessageDialog(null, String.format("You win a discount coupon of $" + String.format("%.2f", (groceriesCost*tier1)) +
                                                ". (8% of your purchase.)"));
        else if (groceriesCost>=60.00 && groceriesCost<=149.99) //tier 2 coupon
            JOptionPane.showMessageDialog(null, String.format("You win a discount coupon of $" + String.format("%.2f", (groceriesCost*tier2)) +
                                                ". (10% of your purchase.)"));
        else if (groceriesCost>=150.00 && groceriesCost<=209.99) //tier 3 coupon
            JOptionPane.showMessageDialog(null, String.format("You win a discount coupon of $" + String.format("%.2f", (groceriesCost*tier3)) +
                                                ". (12% of your purchase.)"));
        else if (groceriesCost>=210.00) //tier 4 coupon
            JOptionPane.showMessageDialog(null, String.format("You win a discount of $" + String.format("%.2f", (groceriesCost*tier4)) +
                                                ". (14% of your purchase.)"));

        System.exit(0);
    }
}

Answer 1

您不应格式化整个字符串。只有双人间。

 JOptionPane.showMessageDialog(null, "You win a discount coupon of $" + String.format("%.2f", (groceriesCost*tier1)) +
                                            ". (8% of your purchase.)");

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